The Stealth War: Host Parasite Coevolution

  • Grade 11th
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| Questions: 20 | Updated: Mar 9, 2026
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1. The process where a parasite changes its surface proteins to stay ahead of the host's immune system is called ______ variation.

Explanation

If the host's immune system learns to recognize a specific protein, then the parasite must switch to a new protein "mask" to stay hidden. This constant switching is a key feature of coevolution.

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About This Quiz
The Stealth War: Host Parasite Coevolution - Quiz

This quiz covers host-parasite coevolution and consists of 20 questions designed for students in Grade 11. You will explore key concepts like adaptation, natural selection, and the strategies that parasites and hosts use to survive. Understanding these interactions is important because they shape ecosystems and influence species' survival. As you... see moretake this quiz, you�ll gain insights into the intricate balance of life and the ongoing 'stealth war' between hosts and parasites. By the end, you'll enhance your knowledge and be better prepared for discussions in biology class.
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2. Which summary best describes the outcome of host parasite coevolution?

Explanation

If the host develops a defense, the parasite adapts; if the parasite adapts, the host must develop a new defense. This reciprocal pressure creates a never-ending cycle of change.

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3. The ______ theory suggests that sex evolved primarily to help hosts stay ahead of their rapidly evolving parasites.

Explanation

If parasites are the most rapidly changing threat in nature, then hosts need a way to change their children's DNA quickly. If sexual recombination provides this speed, then the Red Queen hypothesis explains the advantage of sex.

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4. If a host becomes 100% resistant to a parasite, the coevolutionary cycle ends and the parasite goes extinct.

Explanation

If the parasite can no longer infect any members of the host species and has no other hosts available, then it cannot reproduce. If it cannot reproduce, then its lineage will vanish from the environment.

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5. Which of the following can occur during a coevolutionary arms race?

Explanation

If the host gets a better shield and the parasite gets a better sword, then the traits "escalate." If they become so specialized they can only interact with each other, then they reach an evolutionary extreme.

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6. Why does sexual reproduction help hosts in the context of host parasite coevolution?

Explanation

If an asexual host produces identical clones, then a parasite that "cracks the code" for one will kill them all. If sexual reproduction shuffles the genes, then every offspring has a slightly different "lock" on their cells.

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7. A mutation that provides a host with resistance to a parasite is an example of a(n) ______ trait that will likely become more common in the population.

Explanation

If a host survives because of a new genetic trait while others die, then that trait is beneficial for that specific environment. If a trait increases survival, then it is an adaptation.

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8. Host parasite coevolution often results in a "geographic mosaic" where different areas have different levels of resistance and virulence.

Explanation

If a parasite is very active in one forest but absent in another, then the hosts in the first forest will evolve faster. If the environments differ, then the "arms race" will be at different stages in different locations.

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9. Which of the following are examples of "counter-defenses" used by parasites?

Explanation

If the host develops a block, then the parasite must find a workaround, such as disabling the host's "alarm" chemicals or mutating its own attachment tools to fit new receptors.

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10. What is the "cost of resistance" in host parasite coevolution?

Explanation

If a host builds a complex immune system, then it must use calories that could have gone toward making more offspring. If the environment is free of parasites, then the "expensive" immune system may actually be a disadvantage.

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11. What is the fundamental definition of host parasite coevolution?

Explanation

If a host evolves a defense and the parasite subsequently evolves a way to bypass that specific defense, then both species are influencing each other's genetic traits over time.

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12. Vertical transmission (parent to offspring) usually leads to higher virulence than horizontal transmission (host to host).

Explanation

If a parasite is passed to the offspring, then it depends on the parent surviving and reproducing. If the parasite kills the parent too soon, it cannot be passed on; therefore, vertical transmission usually leads to lower virulence.

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13. How does host parasite coevolution impact the fitness of the species involved?

Explanation

If the host must use energy to fight infection and the parasite must use energy to bypass immunity, then both face a "cost" of coevolution. If multiple defense/attack strategies exist in the population, then genetic diversity (polymorphism) increases.

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14. In brood parasitism (like Cuckoos), what is the "counter-defense" evolved by the host birds?

Explanation

If a cuckoo lays an egg that looks like the host's eggs, then the host might raise a stranger. If the host evolves better vision to spot the slightly different patterns, then it can throw the parasite egg out of the nest.

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15. Some parasites use molecular ______ to mimic the host's own proteins, making it difficult for the immune system to detect the invader.

Explanation

If a parasite can look chemically identical to the host's own cells, then the immune system will not attack it. If this "disguise" is effective, then the parasite can thrive undetected.

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16. Host parasite coevolution is a primary driver of the "Red Queen" dynamic where species must constantly adapt to survive.

Explanation

If a parasite is always finding new ways to infect, then the host is never "finished" evolving its defenses. If both are constantly changing to keep up with the other, then they are in a Red Queen race.

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17. Why did the Myxoma virus in Australian rabbits become less deadly over several years?

Explanation

If a virus is extremely lethal, then it kills the host before mosquitoes can bite and transfer the virus to another rabbit. If the virus evolves to be less lethal, then it has a longer window of time to be transmitted.

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18. Which of the following are common host defenses involved in host parasite coevolution?

Explanation

If a host is under constant attack, then it must utilize chemical, physical, and behavioral tools to survive; however, animal hosts do not perform photosynthesis.

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19. The degree of harm caused by a parasite to its host is known as ______ , which often decreases over time to ensure the parasite doesn't kill its host too quickly.

Explanation

If a parasite kills its host before it can spread to a new one, then the parasite's lineage will end; therefore, natural selection often favors a balance in how deadly the parasite is.

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20. In host parasite coevolution, the parasite acts as a selective pressure that favors hosts with better immune defenses.

Explanation

If parasites reduce the survival or reproduction of the host, then only those hosts with resistant traits will live to pass on their genes.

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The process where a parasite changes its surface proteins to stay...
Which summary best describes the outcome of host parasite coevolution?
The ______ theory suggests that sex evolved primarily to help hosts...
If a host becomes 100% resistant to a parasite, the coevolutionary...
Which of the following can occur during a coevolutionary arms race?
Why does sexual reproduction help hosts in the context of host...
A mutation that provides a host with resistance to a parasite is an...
Host parasite coevolution often results in a "geographic mosaic" where...
Which of the following are examples of "counter-defenses" used by...
What is the "cost of resistance" in host parasite coevolution?
What is the fundamental definition of host parasite coevolution?
Vertical transmission (parent to offspring) usually leads to higher...
How does host parasite coevolution impact the fitness of the species...
In brood parasitism (like Cuckoos), what is the "counter-defense"...
Some parasites use molecular ______ to mimic the host's own proteins,...
Host parasite coevolution is a primary driver of the "Red Queen"...
Why did the Myxoma virus in Australian rabbits become less deadly over...
Which of the following are common host defenses involved in host...
The degree of harm caused by a parasite to its host is known as ______...
In host parasite coevolution, the parasite acts as a selective...
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